Abstract Magnetoresistance in underdoped ( T c=120 K) HgBa 2Ca 2Cu 3O 8 films prepared by a sol–gel method on Y 0.15Zr 0.85O 1.93 substrates was measured as function of field and temperature. In the temperature range 25–50 K, the resistivity is linearly dependent on the magnetic field and is dominated by thermally activated flux creep. The average activation energy required for flux depinning was estimated for several fields using the Anderson–Kim model. The depinning potential U and the critical resistivity ρ c are field dependent and decrease with external magnetic field. For fields of up to 17 T, U varies from 0.026–0.016 eV. The magnetoresistance was studied for H‖c and H‖ab configurations to reveal the anisotropy. Steps in ρ vs. H were observed at low temperatures at the resistance onset. These steps are probably due to inhomogeneous distribution of the field inside the film.